Will fluorescent materials produce harmful radiation

From fireflies to fluorescent rods, fluorescence is very common in our lives, and new products such as fluorescent brighteners and luminous watches are gradually entering people's lives. When people's contact with fluorescent materials continues to deepen, they also have many questions about the safety of their products - will they emit harmful radiation?


What is fluorescent material


Generally speaking, fluorescent material refers to a kind of material that can emit some visible light after being irradiated by electron beam or light (ray) with specific frequency. For example, it is often seen at the crime scene that Luminol reagent, which is used to test blood stains, reacts with iron in blood (heme) and emits blue fluorescence when irradiated with ultraviolet light.


As early as 1575, it was observed that the yellow aqueous solution of Philippine rosewood slices presented a lovely sky blue under the sun. In 1852, G.G. Stokes observed quinine and chlorophyll solutions with a spectrometer and found that the wavelength of the light they emitted was slightly longer than the wavelength of the incident light. From this, it was determined that this phenomenon was caused by the absorption of light energy and the re emission of light of different wavelengths, rather than the diffusion of light. Stokes called this light fluorescence.


After about 50 years of development, fluorescent materials with rare earth compounds as raw materials have the tendency to replace traditional fluorescent materials and become mainstream due to their strong absorption capacity, high conversion rate, stable physical and chemical properties, rich energy levels and 4f electron transitions.


How does fluorescence come out


Fluorescence is the radiation emitted when a substance is inactivated from the excited state to a low energy state with the same multiplicity. * It is common to absorb ultraviolet light and emit visible light. The basic condition for a compound to produce fluorescence is that the energy absorbed when it undergoes a multiplicity invariant transition is less than the energy required to break weak chemical bonds. Secondly, there must be fluorescent groups in the structure of the compound, such as=C=O, - N=O, - N=N,=C=N,=C=S, etc.


For molecules with fluorescence characteristics, after absorbing the energy of incident light, the electrons inside are like rabbits running in the forest, running from the ground state S0 to the excited state S2 with the same spin multiplicity [5] (essentially electronic transition): S0+hvex → S2 (h is the Planck constant, and vex is the frequency of incident light photons). The excited electrons can release their energy to return to the ground state through various ways: for example, the electrons can go through a very fast internal conversion process from S2 (the process takes less than 10-12 seconds), jump to the excited state S1 with slightly lower energy and the same spin multiplicity without emitting any radiation, and then release energy from S1 to return to the ground state S0: S1 → S0+hvf in a luminous way, So we see fluorescence.


For light-emitting cells, fluorescence is the "product" of oxidation reaction, so the necessary condition is an aerobic environment. Luminescent enzymes and aldehydes in cells react together with the participation of oxygen and energy materials (from flavin mononucleic acid, different from fireflies) to emit fluorescence, which is called biofluorescence.


The fluorescence in our life


Luminous paint (material)


Luminous paint refers to a kind of material that can emit various colors of fluorescence in the dark. It can be divided into two types: self luminous type and light storing type. The basic composition of self luminous luminous materials is radioactive materials, which do not need to absorb energy from the outside, and can emit light continuously. Its radioactivity may cause certain harm to human body (depending on the composition), so its application is greatly limited; Light storing luminous materials rarely use radioactive materials, mainly by absorbing external light energy and slowly releasing it. In addition, sufficient light energy must be stored to give light for a period of time. The use is basically unrestricted, but the brightness is not as good as that of self luminous materials.


In recent years, the light storage materials have developed towards the non radiation direction. The brightness of the light storage materials made of aluminum, barium strontium doped rare earth elements and sintered at high temperature is hundreds of times higher than that of traditional materials.


Reflective material


This material is widely used in various traffic signs* It was long ago that Dr. Dong Qifang, an American Chinese scientist, developed directional glass beads, and then all kinds of reflective sheeting, reflective films and reflective coatings came out one after another. In fact, the current traffic signs are divided into two categories: one is reflective materials, which rely on reflecting the incident light back to achieve warning purposes; The other is photoluminescence, which can not only reflect light, but also radiate photons when exposed to light. It looks more eye-catching than ordinary reflective materials, such as chalcogenide materials. These usually do not produce radiation harmful to human body, but whether it has chemical toxicity depends on the specific analysis of specific components.


Fluorescent rod and fluorescent key chain


The fluorescent rods that must be used in festival parties and various concerts are mainly composed of three substances: peroxides, ester compounds and fluorescent dyes. Shake it for a few times or shake it for a few times. The peroxide reacts with the ester compound, and then transfers the energy after the reaction to the fluorescent dye. After that, the dye emits fluorescence. The whole process will not emit radiation harmful to the human body. Although the fluorescent rod will not emit harmful rays, the liquid inside is not edible, and contact with skin, especially eyes, should be avoided as far as possible. So, as long as you don't use knives and scissors to destroy and twist the fluorescent rod, take it and shake it heartily!


A similar principle applies to fluorescent keychains. As long as you don't use it violently as you use the fluorescent rod, it will only bring convenience to you, and the potential danger still comes from the toxicity of the chemical components inside rather than radiation.


A little knowledge about the fluorescent rod is attached: the length of the fluorescent rod's luminous time is inversely proportional to the ambient temperature, that is, the higher the ambient temperature, the shorter the luminous time of the fluorescent rod. When the fluorescent stick in your hand becomes dark, you can put it in the refrigerator or freezer. The low temperature environment can inhibit the chemical reaction of the two liquids, and you can take it out when necessary, so that it can be reused.


Fluorescent brightener


In order to make the paper look white, some businesses will add fluorescent brighteners, or fluorescent bleach, which is a complex organic compound. This whitening agent absorbs ultraviolet light and emits blue light, which is complementary to the yellow light of the paper to form white, so as to achieve whitening effect. It is widely used in paper making, textile, detergent and other fields. This substance will not cause harmful radiation to people, but if you are hungry when reading, do not put paper in your mouth to avoid possible chemical toxicity.


Fluorescent lamp


The luminous principle of the fluorescent lamp is that the fluorescent tube is filled with argon neon mixed gas and mercury vapor, the discharge of the lamp tube makes mercury emit light in the ultraviolet band, and the phosphorous fluorescent paint on the inner surface of the lamp tube absorbs ultraviolet light, and emits fluorescence of different colors depending on the proportion of phosphorous components. The phosphorous fluorescent paint on the inner surface of the lamp tube absorbs most of the ultraviolet light during the lighting process. Under normal circumstances, qualified fluorescent lamps are used. Even if there are some tiny cracks on the fluorescent paint coating, the health risk of using fluorescent lamps will not be increased.


Natural fluorescence


Fireflies are hard to see in cities now. It is amazing that there is no way to soak up paper in the future. The luminescence of fireflies, in short, is a series of complex biochemical reactions catalyzed by fluorescein, and one of the reaction products is the light on their farts. The lovely animals won't be harmful to you, as long as you don't eat what you see.


*Light is also a fluorescence phenomenon in the upper atmosphere* Light is the radiance caused by the solar wind entering the earth's magnetic field. It's too late for everyone to be excited to see the light.


Fluorite and calcite containing some rare earth elements can also emit fluorescence, but the rare earth content is low, and they will not be exposed every day. The harmful radiation is very small, as long as you do not wear it in your arms, hands, feet, neck.


money


*Of course, the popular ones will show up later! In fact, what we want to say here is the printing anti-counterfeit technology - at present, most countries' banknotes, certificates and other items that need to be anti-counterfeit will use special inks to emit fluorescence under ultraviolet light to prevent counterfeiting, and the figure that appears when the ultraviolet lamp is used to illuminate the RMB! Of course, the use of this ink is also safe and harmless. If you still don't believe it, I'll be happy to keep it for you.


conclusion


In general, the fluorescence emitted by common fluorescent materials is non radioactive light, which will not cause harmful radiation to human body. The reason why there is a view that fluorescent substances can harm human body is that radioactive substances, such as tritium gas and β The mixture of tritium, yellow phosphorus and zinc sulfide used in the lamp.


Thankfully, tritiated β Decay only emits electrons that move at high speeds (i.e β Particles), the penetration ability is very weak, and even the thin plexiglass sheet cannot pass through, let alone penetrate the human body, so it is harmful to human body only when inhaled in large quantities.